import { HttpService } from "@nestjs/axios";
import { Injectable } from "@nestjs/common";
import { map, take } from "rxjs";
import { EsResponseDto } from "src/core/domain/dtos";
import { SearchResultDto } from "src/core/domain/dtos/search-result.dto";

/**
 * Search service provider
 */
@Injectable()
export class SearchService {
    /**
     * Constructs the service with injection of
     * HTTPService instance
     * @param httpService 
     */
    constructor(private readonly httpService: HttpService) {}

    /**
     * Elastichsearch server port-number
     */
    private readonly ES_PORT = process.env.ES_PORT;
    
    /**
     * Finds a paper by its own ID
     * @param uuid 
     * @returns Elasticsearch hits or an error object
     */
    async findByID(uuid: string): Promise<SearchResultDto> { // Should I change 'object' to specific DTO?
        let es_query = {
            query: {
                query_string: {
                    query: 'id:' + uuid
                }
            }
        }

        return new Promise((resolve, reject) => {
            try {
                (this.httpService.get<EsResponseDto>('http://localhost:' + this.ES_PORT + '/_search', {
                    data: es_query,
                    headers: {'Content-Type': 'application/json'},
                }))
                .pipe(take(1), map(axiosRes => axiosRes.data))
                .subscribe((res: any) => {
                    if (res.timed_out) {
                        reject(new SearchResultDto(504, {message: 'Timed Out'}));
                    }

                    if (!res.hits.hits.length) {
                        reject(new SearchResultDto(404, {message: 'Not Found'}));
                    }

                    resolve(new SearchResultDto(200, res.hits));
                });
            } catch (error) {
                reject(new SearchResultDto(700, error));
            }
        });
    }

    /**
     * Finds relevant documents by context using the given query string
     * @param query_str 
     * @returns Elasticsearch hits or an error object
     */
    async findByContext(query_str: string): Promise<SearchResultDto> {
        let es_query = {
            query: {
                query_string: {
                    query: query_str,
                    default_field: "content"
                }
            }
        }

        return new Promise((resolve, reject) => {
            try {
                (this.httpService.get<EsResponseDto>('http://localhost:'+ this.ES_PORT + '/_search', {
                    data: es_query,
                    headers: {'Content-Type': 'application/json'},
                }))
                .pipe(take(1), map(axiosRes => axiosRes.data))
                .subscribe((res: any) => {
                    if (res.timed_out) {
                        reject(new SearchResultDto(504, {status: 504, message: 'Timed Out'}));
                    }

                    if (!res.hits.hits.length) {
                        reject(new SearchResultDto(404, {status: 404, message: 'Not Found'}));
                    }                

                    resolve(new SearchResultDto(200, res.hits));
                });
            } catch (error) {
                reject(new SearchResultDto(700, error));
            }
        });
    }
}